Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum Quarry: Scientists Unveil New Technique for Spotting Quantum Dots to Make High Performance Nanophotonic Devices

13.08.2015

An international team of scientists, including Dr Luca Sapienza from the University of Southampton, have developed a new technique for finding quantum dots.

A quantum dot should produce one and only one photon—the smallest constituent of light—each time it is energized, and this characteristic makes it attractive for use in various quantum technologies, such as secure communications. However, the trick is in finding them.


Circular grating geometry for efficiently extracting single photons from a quantum dot.

While they appear randomly, in order for the dots to be useful they need to be located in a precise relation to some other photonic structure, be it a grating, resonator or waveguide, which will enable control of the photons that the quantum dot generates. However, finding the quantum dots—they’re just about 10 nanometers across—is no small feat.

Now, researchers working at the National Institute of Standards and Technology (NIST) in the United States, in collaboration with the universities of Southampton (UK)and Rochester (US), have developed a simple new technique for locating them and used it to create high-performance single photon sources.

This new development, which is published in Nature Communications, may make the manufacture of high-performance photonic devices using quantum dots much more efficient. Such devices are usually made in regular arrays using standard nanofabrication techniques like electron-beam lithography and semiconductor etching.

However because of the random distribution of the dots, only a small percentage of them will line up correctly, at the optimum position within the device. This overall process thus produces very few working devices.

“This is a first step towards providing accurate location information for the manufacture of high performance quantum dot devices,” says NIST physicist Kartik Srinivasan. “So far, the general approach has been statistical - make a lot of devices and end up with a small fraction that work - but our camera-based imaging technique instead seeks to map the location of the quantum dots first, and then uses that knowledge to build optimized light-control devices in the right place.”

Dr Luca Sapienza, from the University’s Quantum Light and Matter group, says: “This new technique is sort of a twist on a red-eye reducing camera flash, where the first flash causes the subject’s pupils to close and the second illuminates the scene.”

In their setup, instead of xenon-powered flash the team used two LEDS. One LED activates the quantum dots when it flashes (you could say this LED gives the quantum dots red eye). At the same time, a second, different color LED flash illuminates metallic orientation marks placed on the surface of the semiconductor wafer the dots are embedded in. Then a sensitive camera snaps a 100-micrometer by 100-micrometer picture.

By cross-referencing the glowing dots with the orientation marks, the researchers can determine the dots’ locations with an uncertainty of less than 30 nanometers. Their coordinates in hand, scientists can then tell the computer-controlled electron beam lithography tool to place any structure the application calls for in its proper relation to the quantum dots, resulting in many more usable devices.

Using this technique, the researchers demonstrated grating-based single photon sources in which they were able to collect 50 per cent of the quantum dot’s emitted photons, the theoretical limit for this type of structure.

They also demonstrated that more than 99 per cent of the light produced from their source came out as single photons. Such high purity is partly due to the fact that the location technique helps the researchers to quickly survey the wafer (10,000 square micrometers at a time) to find regions where the quantum dot density is especially low–only about one per 1,000 square micrometers. This makes it far more likely that each grating device contains one—and only one—quantum dot.

This work was performed in part at NIST’s Center for Nanoscale Science and Technology (CNST), a national user facility available to researchers from industry, academia and government.

Ends

Notes for editors:
1. L. Sapienza, M. Davanço, A. Badolato and K. Srinivasan. Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission. Nature Communications, 6, 7833 doi:10.1038/ncomms8833. Published 27 July 2015.
2. The attached image shows circular grating geometry for efficiently extracting single photons from a quantum dot.
3. Through world-leading research and enterprise activities, the University of Southampton connects with businesses to create real-world solutions to global issues. Through its educational offering, it works with partners around the world to offer relevant, flexible education, which trains students for jobs not even thought of. This connectivity is what sets Southampton apart from the rest; we make connections and change the world. http://www.southampton.ac.uk/ 
http://www.southampton.ac.uk/weareconnected
#weareconnected


For further information:
Glenn Harris, Media Relations, University of Southampton, Tel 023 8059 3212, email G.Harris@soton.ac.uk, Twitter: @glennh75
www.soton.ac.uk/mediacentre/
Follow us on twitter: http://twitter.com/unisouthampton
Like us on Facebook: www.facebook.com/unisouthampton

Contact Information
Steve Williams
Media Contact
s.williams@soton.ac.uk

Steve Williams | newswise

Further reports about: LED Performance QUANTUM quantum dot single photon sources single photons structure

More articles from Physics and Astronomy:

nachricht NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center

nachricht Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>